This invention relates to security systems and more particularly to apparatus and methods for communicating between individual components of the security system which are not otherwise linked.
Electronic security systems for controlling access to one or more secure areas are well known. Such security systems at first incorporated one or more electronic locks to secure a desired area and a magnetically, mechanically or electronically encoded key. In operation, if the code on the key matched the code stored in the lock, then the lock would open. However, the combination code of the lock in such systems was generally difficult to change and therefore provided little increase in security for hotels and the like where it was desired to change the combination code in the electronic lock each time the room was assigned to a new guest.
In order to solve this problem, various systems were devised which would enable the combination of the lock to be changed in response to the coding on a new key card. One such security system was disclosed in Sabsay, U.S. Pat. No. 3,821,704 issued June 28, 1974 and reissued as U.S. Pat. No. Re. 29,259 on June 7, 1977. In that patent, a central console is provided for encoding key cards with two data fields. Each lock is programmed to sense the data in the two fields on the card and to change the combination code in the lock if a particular matching sequence between the old combination code stored in the lock and the two fields of data stored on the key card is satisfied. Of course, all combination codes for all locks in the system also had to be stored in the memory of the central console to enable the key cards to be properly encoded.
While Sabsay provided a security system with practical application in facilities such as hotels, various disadvantages still existed. For example, Sabsay did not address the problem of how to synchronize each of the locks so that the combination code in each lock corresponded to the combination code for that lock stored in the central console.
In order to overcome this and other problems which hindered practical implementation of the Sabsay system, the security system of Genest et al. Pat. No. 4,283,710 was devised to include a permanent security override module and a temporary security override module which enabled the combination code for a particular lock to be loaded from the console into a memory in the module. The module could then be carried to and inserted in an out-of-sync lock with the data stored therein and transferred into and stored in the lock in place of the out-of-sync code combination. The Genest override modules additionally permitted various other functions to be performed to enable a practical implementation of a security system in a facility such as a hotel.
However, the Genest security system involved an inherent security weakness in that the communication link between the console and programmer and between the programmer and lock was not secure. This weakness resulted because the Genest security modules were simply conduits for the combination codes whereby a particular combination code was transferred from the console to the security module and thereafter transferred from the security module to the lock. Therefore, an unauthorized person could "read" the data in the security module memory and be able to determine what the combination code of a particular lock was.
In order to overcome this security weakness, the present invention provides a novel security system whereby the programmer device receives a coded data word from the console and then prior to transferring the coded data word to the lock, but only after the console coded programmer has been inserted into communication with the lock, decodes and in some instances further encodes the coded data word which is then transferred to the lock. The lock is then preprogrammed to reverse the encoding to obtain the desired combination code. Therefore, an unauthorized person "reading" the memory from the console coded programmer would be unable to derive the combination code without knowing first the encoding routine performed on the data word by the console prior to transferring the data word to the console coded programmer and second the decoding and in some instances further encoding operation performed by the programmer processor.
Therefore, the console coded programmer of the present invention, unlike the security module of Genest et al., is not merely a conduit but is an active processing device which manipulates the data words stored therein in one or more predefined ways prior to transferring the data word to the lock.
Further, in accordance with the invention, in the embodiment where the programmer further modifies the data word, the individual locks in the system are also programmed to decode the modified data word received from the console coded programmer by reversing both the encoding performed by the programmer and the encoding performed by the console. Hence, in that embodiment, an unauthorized person who is able to obtain a word from the programmer after the programmer had performed its encoding and decoding operations would still be unable to decipher the value of the combination code because that person could not derive the decoding routine programmed to be performed by the lock. Therefore, the present system provides significantly increased security in the data transmission link between the console, console coded programmer and individual locks.